C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  How Do I overload (TYPE) operator?          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message sean worlock Guest Posted: Thu Oct 28, 2004 2:10 pm    Post subject: How Do I overload (TYPE) operator? I have written a simple class that modals the action of a complex number. This class is called CComplex. I wish to make my class as versatile as possable. Thus lets say I have some variables defined as following: int value1; double value2; float value3; and three Complex objects defined as: CComplex ONE,TWO,THREE; I wish to perform the following... ONE=(CComplex) value1; TWO=(CComplex) value2; THREE=(CComplex) value3; thus I need to create a type operator for my CComplex class. I have read many texts for the conversion of my class into other types but not the other way. could anybody point me in the correct direction for the prototype and function syntax to complete this? [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Thomas Mang Guest Posted: Fri Oct 29, 2004 2:13 am    Post subject: Re: How Do I overload (TYPE) operator? "sean worlock" <sean_worlock (AT) sworlock (DOT) freeserve.co.uk> schrieb im Newsbeitrag news:clom3l$746$1 (AT) newsg2 (DOT) svr.pol.co.uk... Quote: I have written a simple class that modals the action of a complex number. This class is called CComplex. I wish to make my class as versatile as possable. Thus lets say I have some variables defined as following: int value1; double value2; float value3; and three Complex objects defined as: CComplex ONE,TWO,THREE; I wish to perform the following... ONE=(CComplex) value1; TWO=(CComplex) value2; THREE=(CComplex) value3; thus I need to create a type operator for my CComplex class. I have read many texts for the conversion of my class into other types but not the other way. You mean an implicit (that is, not 'explicit') constructor? class CComplex { public: CComplex(); CComplex(int SomeInt); // note: implicit conversion possible }; Then you simply write ONE = value1; value1 will be used to convert the int into a CComplex, which will then be assigned to ONE. Another alternative is, of course, to overload operator= for various types. Thomas [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top jakacki Guest Posted: Fri Oct 29, 2004 2:16 pm    Post subject: Re: How Do I overload (TYPE) operator? Quote: I have written a simple class that modals the action of a complex number. This class is called CComplex. I wish to make my class as versatile as possable. Thus lets say I have some variables defined as following: int value1; double value2; float value3; and three Complex objects defined as: CComplex ONE,TWO,THREE; I wish to perform the following... ONE=(CComplex) value1; TWO=(CComplex) value2; THREE=(CComplex) value3; Add constructors from desired types: class CComplex { .... CComplex(int i) .... CComplex(double d) .... CComplex(float f) .... .... }; Moreover, your assignments would be better written as constructions, not conversions: ONE = CComplex(value1); TWO = CComplex(value2); THREE = CComplex(value3); And if it is the first place you use the variables, you can do even better by writting the above as declarations (that way you avoid gratituous copy assignments): CComplex ONE(value1); CComplex TWO(value2); CComplex THREE(value3); If you don't want your newly defined ctors to take part in automatic conversions (and automatic conversions are often misleading to programmers), do this: .... explicit CComplex(int) .... ^^^^^^^^ .... HTH Grzegorz PS: It is common style to use ALL_CAPS identifiers for macros only. -- Free C++ frontend library: http://opencxx.sourceforge.net China from the inside: http://www.staryhutong.com Myself: http://www.dziupla.net/gj/cv [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Sven Rosiers Guest Posted: Fri Oct 29, 2004 2:32 pm    Post subject: Re: How Do I overload (TYPE) operator? sean worlock wrote: Quote: I have written a simple class that modals the action of a complex number. This class is called CComplex. I wish to make my class as versatile as possable. Why not use the std::complex template from the standard library? [SNIP] Quote: CComplex ONE,TWO,THREE; I wish to perform the following... ONE=(CComplex) value1; TWO=(CComplex) value2; THREE=(CComplex) value3; Don't use C-style casts in a C++ program. Use C++-style casts instead. Quote: thus I need to create a type operator for my CComplex class. I have read many texts for the conversion of my class into other types but not the other way. could anybody point me in the correct direction for the prototype and function syntax to complete this? Conversion of an object of some other type into an object of your class is achieved with a conversion constructor (that is, a constructor that can be called with a single parameter that is not marked explicit), like so: class my_class { public: my_class(int); }; This allows the compiler to implicitly convert an int into an object of my_class whereever it needs to. Sven R. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Peter Koch Larsen Guest Posted: Fri Oct 29, 2004 2:32 pm    Post subject: Re: How Do I overload (TYPE) operator? "sean worlock" <sean_worlock (AT) sworlock (DOT) freeserve.co.uk> skrev i en meddelelse news:clom3l$746$1 (AT) newsg2 (DOT) svr.pol.co.uk... Quote: I have written a simple class that modals the action of a complex number. This class is called CComplex. You should use the standard complex class instead, but assuming this is just an exercise..... Quote: I wish to make my class as versatile as possable. Thus lets say I have some variables defined as following: int value1; double value2; float value3; and three Complex objects defined as: CComplex ONE,TWO,THREE; I wish to perform the following... ONE=(CComplex) value1; TWO=(CComplex) value2; THREE=(CComplex) value3; Avoid the C-like way of converting between different types. This is practically never necessary in C++. Also do not use all capitals for your variable names (this should be reserved for macros), Quote: thus I need to create a type operator for my CComplex class. I have read many texts for the conversion of my class into other types but not the other way. It is called the constructor. class CComplex { ...... CComplex(double) {... } ..... this lets you write the above the assignments. /Peter [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Thomas Richter Guest Posted: Fri Oct 29, 2004 2:33 pm    Post subject: Re: How Do I overload (TYPE) operator? Hi, Quote: I have written a simple class that modals the action of a complex number. This class is called CComplex. I wish to make my class as versatile as possable. Thus lets say I have some variables defined as following: int value1; double value2; float value3; and three Complex objects defined as: CComplex ONE,TWO,THREE; I wish to perform the following... ONE=(CComplex) value1; TWO=(CComplex) value2; THREE=(CComplex) value3; thus I need to create a type operator for my CComplex class. This is not a type operator, this is rather a constructor from int, double or float objects. Thus: class CComplex { double re,im; Complex(double v) : re(v), im(0.0) { } Complex(float v) : re(v), im(0.0) { } Complex(int v) : re(v), im(0.0) { } // // more to go here... }; should do it. Then you'd be able to write. ONE = 1; and ONE = CComplex(1); As a side remark, it is not wrong, but against all good traditions to use all-upper case names for objects. So long, Thomas [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ron Samuel Klatchko Guest Posted: Fri Oct 29, 2004 2:38 pm    Post subject: Re: How Do I overload (TYPE) operator? "sean worlock" <sean_worlock (AT) sworlock (DOT) freeserve.co.uk> wrote Quote: I have written a simple class that modals the action of a complex number. This class is called CComplex. I wish to make my class as versatile as possable. Thus lets say I have some variables defined as following: int value1; double value2; float value3; and three Complex objects defined as: CComplex ONE,TWO,THREE; I wish to perform the following... ONE=(CComplex) value1; TWO=(CComplex) value2; THREE=(CComplex) value3; thus I need to create a type operator for my CComplex class. I have read many texts for the conversion of my class into other types but not the other way. could anybody point me in the correct direction for the prototype and function syntax to complete this? You can think of that operation in two ways. One is converting from an int to a complex. The other is constructing a complex from an int. Since you have no control over int, you can't create a cast for it. But you can create new constructors for your complex type: class CComplex { public: CComplex(int); CComplex(double); ... samuel [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Allan W Guest Posted: Fri Oct 29, 2004 2:39 pm    Post subject: Re: How Do I overload (TYPE) operator? "sean worlock" <sean_worlock (AT) sworlock (DOT) freeserve.co.uk> wrote Quote: I have written a simple class that modals the action of a complex number. This class is called CComplex. I wish to make my class as versatile as possable. I wish to perform the following... ONE=(CComplex) value1; // an integer TWO=(CComplex) value2; // a double THREE=(CComplex) value3; // a float thus I need to create a type operator for my CComplex class. You need to overload your constructors. class CComplex { double r, i; public: explicit CComplex(double real=0.0, double imag=0.0) : r(real),i(imag) {} explicit CComplex(const CComplex&t) : r(t.r) ,i(t.i) {} explicit CComplex(int real, int imag=0) : r(real),i(imag) {} explicit CComplex(float real, float imag=0.0f) : r(real),i(imag) {} // more stuff... }; The first constructor is the default constructor, because all arguments have default values. It also accepts either one or two double values, so that you're able to initialize TWO above. The second constructor is a copy constructor, used whenever the compiler needs to copy a CComplex object -- for instance when a function returns CComplex by value. Frankly, you don't need the other two constructors because ints and floats can already be converted to double. I included them because it demonstrates the technique you're looking for. Note that you can only have one default constructor -- don't make the first argument optional in any of the other constructors, or you'll get ambiguity errors. You would probably want to do something similar with operator= as well. See any book on C++ for examples on how to do this. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Alberto Barbati Guest Posted: Fri Oct 29, 2004 2:40 pm    Post subject: Re: How Do I overload (TYPE) operator? sean worlock wrote: Quote: I have written a simple class that modals the action of a complex number. This class is called CComplex. I wish to make my class as versatile as possable. Thus lets say I have some variables defined as following: int value1; double value2; float value3; and three Complex objects defined as: CComplex ONE,TWO,THREE; First of all, using ALL CAPS for variable is not good programming style. Common practice is to use all caps identifiers for macros only. Quote: I wish to perform the following... ONE=(CComplex) value1; TWO=(CComplex) value2; THREE=(CComplex) value3; C-style casts are also bad programming style, you should avoid them at all costs. Use C++ casts, like static_cast<> for example. In this particular case you don't even need casts as: one = value1; two = value2; three = value3; are perfectly valid, once you solve the conversion issue. If you really want to stress the conversion you can use the "functional" style: one = CComplex(value1); two = CComplex(value2); three = CComplex(value3); Quote: thus I need to create a type operator for my CComplex class. I have read many texts for the conversion of my class into other types but not the other way. could anybody point me in the correct direction for the prototype and function syntax to complete this? The term "type operator" is not C++ terminology. I assume you meant "conversion operator". What you need is not conversion operators, but constructors. Just write: class CComplex { public: CComplex(int x) { /*...*/ } CComplex(float x) { /*...*/ } CComplex(double x) { /*...*/ } /*...*/ }; HTH, Alberto [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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